1. Field of the Invention
The present invention relates to a rubbing method and a method and an apparatus for producing an optical film, and particularly to a rubbing method suitable for forming a liquid crystal orientation film for uniformly orienting liquid crystal molecules and a method and an apparatus for producing an optical film to which the rubbing method is applied.
2. Description of the Related Art
Recently, demand for optical films is increasing. Typical examples of such optical films include optical compensation films used as retardation films in liquid crystal cells, antireflection films and antiglare films, which have various functions.
Typical methods of producing such optical films include a method which comprises performing rubbing treatment on the surface of a belt-shaped flexible support (hereinafter referred to as a “web”), applying a coating solution to the surface of the web using various coating apparatuses and drying and then curing the same to form a coated film (functional film) of various compositions.
The rubbing treatment is a typical technique for orienting liquid crystal molecules in the production of liquid crystal display devices, and generally an orientation film is formed on the surface of a web and the surface of the orientation film is rubbed in one direction by a rubbing roller.
In such production of optical films, poor orientation due to unstable rubbing treatment conditions, which is one of the causes of decreased yield, has become a problem. Thus, various proposals have been made in order to reduce such poor orientation (see Japanese Patent Application Laid-Open Nos. 8-160431, 8-160430 and 2002-55345).
Japanese Patent Application Laid-Open No. 8-160431 proposes a construction in which a rubbing roller is disposed between two, transfer rollers and a web is transferred while being wound on the rubbing roller, enabling continuous production.
Japanese Patent Application Laid-Open No. 8-160430 proposes a construction in which a long web is wound around a rubbing roller disposed diagonally to the traveling direction of the web and the traveling direction of the web is changed to perform continuous rubbing. It is described that this technique is capable of uniformly rubbing orientation films.
Japanese Patent Application Laid-Open No. 2002-55345 proposes a construction in which hot air at about a phase transition temperature of SmA-SmC is sprayed to the web through a spray nozzle, and it is described that an orientation film can be uniformly rubbed under heating and pressurization.